This study is designed to determine if combining parathyroid (PTH 1-34) with fluoride (MFPSR) therapy in a cyclic treatment regimen will: (1) produce a greater increase in bone density of the spine than would be produced by either treatment alone; (2) prevent the resistance (i.e., decreased bone formation and no further increase in bone density) that is observed within 18-24 months of PTH therapy; (3) eliminate the calcium deficiency and osteomalacia that can occur with fluoride; (4) prevent excessive bone fluoride content; and (5) result in an increase in bone density which is maintained after treatment is discontinued.